1. Field of the Invention
The present invention relates to the field of asymmetric catalysis. More particularly, the invention relates to the field of organometallic catalysts useful for enantioselectively epoxidizing prochiral olefins and a new class of amid-salicylidene ligands and their metal complexes (i.e. an optically active metal ligand complex catalyst) as novel ligands and novel catalysts.
Asymmetric epoxidation of olefins constitutes an extremely appealing strategy for the synthesis of optically active organic compounds. Several advances in this area have occurred in recent years. The most commonly and successfully used catalysts for asymmetric epoxidation of unfunctionalized olefins are porphyrin and salen based systems. Chiral metal porphyrins have been reported to catalyze asymmetric epoxidation of styrene derivatives with high turnover numbers and moderate enantioselectivities (J. P. Collman et al. Science, 1993, 26, 1404). Unfortunately, the chiral porphyrin systems are usually difficult to prepare and are limited to styrene derivatives as substrates. E. N. Jacobsen (J. Am. Chem. Soc. 1990, 112, 2801 ) and T. Katssuki (Tetrahedron Lett. 1990, 31, 7345) independently reported asymmetric epoxidation of olefins by bleach or iodosobenzene catalyzed by chiral manganese salen complexes. These chiral salen complexes were designed based on Kochi's achiral cationic mangangese salen complex that was reported in 1986 (J. Am. Chem. Soc. 1986, 108, 108, 2309). The salen based catalysts gave very high enantioselectivities for the epoxidation of cis olefins, e.g. cis-beta-methylstyrene and dihydronaphthalene. However, the turnover numbers of these catalysts are typically 10-30, and they are limited to conjugated cis olefins.
Given the broad synthetic utility of chiral epoxides, more efficient catalytic and enantioselective catalysts besides porphyrin and salen systems for asymmetric epoxidation of unfunctionalized olefins are clearly desirable.
2. Description of the Prior Art
The following prior art references are disclosed in accordance with the terms of 37 CFR 1.56, 1.97, and 1.93.
U.S. Pat. No. 4,471,130 discloses methods for asymmetric epoxidation of allylic alcohols.
U.S. Pat. No. 4,594,439 discloses methods for asymmetric epoxidation of carbinals using a titanium catalyst.
U.S. Pat. No. 4,924,011 discloses a process for preparing taxol.
U.S. Pat. No. 5,352,814 discloses methods for asymmetric epoxidation of olefins using an optically active manganese complex.
PCT WO 93/03838 (published Mar. 4, 1993) discloses chiral catalysts useful for epoxidizing prochiral olefins.
PCT WO 93/12260 (published Jun. 24, 1993) discloses a class of asymmetric ligands preferably derived from 2-diphenylphosphinobenzoic acid as an ester or amide from chiral alcohols and chiral amines.
Journal of American Chemical Society, Vol. 110, pages 4087-4089, issued 1988 (ACS), Yoon et al., discloses "Catalysis of Alkene Oxidation by Nickel Salen Complexes Using NaOCl under Phase-Transfer Conditions".
Coordination Chemistry Reviews 140, (1995) pp. 189-214, T. Katsuki; Elsevier Science S.A. discloses salen-manganese complexes as catalysts for asymmetric oxidations of unfunctionalized olefins.
Catalytic Asymmetric Synthesis, Iwao Ojima--Editor (1993), VCH Publishers, Inc., pp. 159-202; "Asymmetric Catalytic Epoxidation of Unfunctionalized Olefins" by Eric N. Jacobsen discloses salen-manganese complexes as catalysts for asymmetric oxidations of unfunctionalized olefins.
Journal of American Chemical Society, Vol. 112, No. 7, pages 2801-2803, issued Mar. 28, 1990 (ACS), Zhang et al., discloses "Enantioselective Epoxidation of Unfunctionalized Olefins Catalyzed by (Salen) Manganese Complexes".
Journal of American Chemical Society, Vol. 113, No. 18, pages 7062-4, issued Aug. 28, 1991 (ACS), Jacobsen et al., discloses "Highly Enantioselective Epoxidation Catalysts Derived from 1,2-Diaminocyclohexane".
Bulletin Chemical Society of Japan, Vol. 56, No. 1, issued January, 1983, Kanatomi, discloses "The Dehydrogenation of Nickel (II) Chelates of rac- and meso- 2,2'-[(1,2-Diphenylethylene)bis(iminomethylene)diphenol and Related Compounds".
Chemistry Letters, issued 1986, pages 1483-6 (The Chemical Society of Japan), Nakajima et al., discloses "Asymmetric Oxidation of Sulfides to Sulfoxides by Organic Hydroperoxides with Optically Active Schiff Base--Oxovanadium (IV) Catalysts".
Journal of American Chemical Society, Vol. 113, No. 17, pages 6703-4, issued August 14, 1991 (ACS), Jacobsen et al., discloses "Electronic Tuning of Asymmetric Catalysts".
All of the above-cited prior art and any other references mentioned herein are incorporated herein by reference in their entirety.